A new paper published today in Nature Climate Change (Sallenger et al 2012) describes the discovery of a global hot spot of sea level rise. The team used a tide gauge database to examine how sea level has changed in the US over the last 70 years. Although globally, average sea level is widely known to be increasing, there is enormous spatial variation in the how it is changing.
The study reports that Cape Hatteras, NC marks the southern tip of the hot spot: smack over the eastern seaboard of the US (Fig. 1), where between 1970 and 2009, average sea level rise was 3.80 mm/yr (±1.06). South of Cape Hatteras, sea level rise during this period was not significantly different from zero (which is not the same as saying it did not change). This spatial variance further highlights the complexity of planning for near-future sea level rise. My state, North Carolina, is spit in half! Clearly a state-level policy wouldn’t do. But on the other hand, these trends might not hold into the future, and local fortunes could be reversed.
The authors tentatively attributed the hot spot to another aspect of global warming; the expected slowdown of the Atlantic Meridional Overturning Current, although see a discussion of other potential explanations here.
Fig. 1. Sea level rise measured with tide gauges for 60-yr time series at locations across North America. source Circles are colour-coded to reflect computed SLRDs; no colour fill indicates SLRDs that are not statistically different from zero. Confidence limits are ±1? and account for serial correlation; 50- and 40-yr time series results are shown in Supplementary Fig. S3.
The study also reported evidence for accelerated sea level rise during the study period in the hot spot, e.g.;